常伊梅林^1,,
唐常源^{1, 2},
李杏^2,,,
李锐²,
曹英杰²
1.中山大学地理科学与规划学院 广州 510275
2.中山大学环境科学与工程学院 广州 510006
基金项目: 广东省基础与应用基础研究专项资金项目2017A030310563
广州市科技计划项目201510010300
国家自然科学基金青年科学基金项目41501512

详细信息

作者简介:常伊梅林, 主要研究方向为土壤重金属污染和土壤氮循环。E-mail:changyimeilin@qq.com

通讯作者:李杏, 主要研究方向为小流域氮循环, 流域地表水、地下水地球化学研究。E-mail:lxbaboon@163.com

中图分类号:X53

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收稿日期:2018-06-19
录用日期:2018-09-12
刊出日期:2019-01-01

Production and release mechanism of N₂O in agricultural soils irrigated with acid mine drainage

CHANG Yimeilin^1,,
TANG Changyuan^{1, 2},
LI Xing^2,,,
LI Rui²,
CAO Yingjie²
1. School of Geography and Planning, Sun Yat-sen University, Guangzhou 510275, China
2. School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China
Funds: the Natural Science Foundation of Guangdong Province, China2017A030310563
the Science and Technology Program of Guangzhou, China201510010300
the National Natural Science Foundation of China41501512

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Corresponding author:LI Xing, E-mail:lxbaboon@163.com

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摘要
摘要:农田系统是温室气体N₂O的主要排放源，目前对酸性矿山废水（acid mine drainage，AMD）灌溉影响下，农田土壤剖面N₂O的来源识别、转换机制及其控制因子缺乏深入研究。本文选择广东省大宝山矿区下游沿岸水稻田和甘蔗田两种典型农田，针对酸性矿山废水灌溉区（上坝村）和天然来水灌溉区（连心村），对土壤理化性质、重金属含量及包气带N₂O浓度、同位素特征值进行了测定，定量计算了硝化和反硝化作用对土壤中N₂O的贡献比和N₂O转化为N₂的还原比，评价了其相关影响因素。结果表明：在AMD影响下，灌区农田土壤剖面N₂O浓度均高于同种作物类型天然来水区土壤，同种灌溉处理下甘蔗田土壤N₂O浓度高于水稻田。甘蔗田表层土壤（0~30 cm）反硝化作用对N₂O产生量的贡献比高于硝化作用，约71.29% N₂O由反硝化作用产生。AMD灌区甘蔗田土壤剖面中N₂O还原成N₂的比例随深度增加逐渐减小，在N₂O浓度峰值处仅有15.54% N₂O被还原成为N₂，而天然来水区N₂O还原成N₂的平均比率高达49.80%。这表明较弱的土壤N₂O还原能力导致较高浓度的N₂O残留在土壤中。相关性分析表明，AMD灌溉通过改变上坝村土壤的pH、重金属含量、含水率从而改变了土壤N₂O的来源途径及还原能力。组合同位素特征值溯源法有效地揭示了农田土壤N₂O的来源和AMD灌区土壤的潜在生态风险，为日后的治理修复工作提供了科学依据。
关键词:同位素特征值/
N₂O/
酸性矿山废水灌溉/
硝化作用/
反硝化作用/
红壤区
Abstract:Acid mine drainage (AMD) is mostly untreated or not up to standard level before directly drained into rivers for irrigation, causing severe pollution of agriculture eco-environments. Metal pollution had been widely reported in extensive fields including the red soil region in South China. As we have known, N₂O emitted from agricultural systems was one of the important causes of global greenhouse effects. However, there has been poor knowledge of potential changes in N₂O evolution in polluted fields. In this study, four agricultural soil profiles from sugarcane and paddy fields were used to track the changes in N₂O emission and sources of heavy metal polluted soils irrigated with AMD (Shangba Village, Wengyuan County, Guangdong Province) and then compared with unpolluted soils irrigated with natural water (Lianxin Village, Wengyuan County, Guangdong Province). The physical/chemical parameters and contents of heavy metals in the soils, N₂O concentration and stable nitrogen and oxygen isotope compositions were analyzed to determine the contribution of nitrification and denitrification of N₂O and the reduction ratio of N₂O. Our results showed that there was slightly higher N₂O concentration of the same crop in AMD irrigated area than in unpolluted soil irrigated with natural water, and higher soil N₂O concentration in sugarcane fields than in rice fields. The production of N₂O from denitrification was 71.29%, which was higher than that from nitrification in surface soil (0-30 cm) in sugarcane fields in areas irrigated with AMD. N₂O reduction ratio in the soil profile in AMD irrigation area decreased gradually with increasing depth. There was only 15.54% N₂O reduction to N₂ at the peak of N₂O concentration. However, the average ratio of N₂O reduction to N₂ in sugarcane fields irrigated with natural water was as high as 49.80%. Limited N₂O reduction led to high levels of N₂O residues in the soil. Studies showed that AMD irrigation changed the production and release of N₂O by changing pH, heavy metal content and moisture content of agricultural soils. N₂O production and reduction studies carried out using combined nitrogen and oxygen isotope compositions clarified potential risks of irrigated agricultural soils with AMD. This provided the scientific basis for future restoration works in polluted soils.
Key words:Isotopic signature/
Nitrous oxide/
Acid mine drainage irrigation/
Nitrification/
Denitrification/
Red soil region

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图1土壤微生物产生N₂O的过程^[6]
Figure1.Microbial sources of N₂O in soil^[6]


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图2酸性矿山废水灌区、天然来水区不同作物田土壤包气带N₂O浓度垂向分布特征
SG:酸性矿山废水灌溉区甘蔗田; SS:酸性矿山废水灌溉区水稻田; LG:天然来水灌溉区甘蔗田; LS:天然来水灌溉区水稻田。
Figure2.Vertical distribution of N₂O concentrations in different crop fields irrigated with acid mine drainage and natural water
SG: sugarcane field in acid mine drainage irrigated area; SS: paddy field in acid mine drainage irrigated area; LG: sugarcane field in natural water irrigated area; LS: paddy field in natural water irrigated area.


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图3酸性矿山废水灌区、天然来水区不同作物田包气带土壤N₂O同位素特征值垂向分布特征
SG:酸性矿山废水灌溉区甘蔗田; SS:酸性矿山废水灌溉区水稻田; LG:天然来水灌溉区甘蔗田; LS:天然来水灌溉区水稻田。SP: ¹⁵N的位嗜值。
Figure3.Vertical distribution of isotope characteristic values of N₂O in the aeration zones of different crop fields irrigated with acid mine drainage and natural water
SG: sugarcane field in acid mine drainage irrigated area; SS: paddy field in acid mine drainage irrigated area; LG: sugarcane field in natural water irrigated area; LS: paddy field in natural water irrigated area. SP: site preference of ¹⁵N.


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图4酸性矿山废水灌区、天然来水区不同作物田土壤SP-δ¹⁸O模型分析的N₂O产生和消耗途径
SG:酸性矿山废水灌溉区甘蔗田; SS:酸性矿山废水灌溉区水稻田; LG:天然来水灌溉区甘蔗田; LS:天然来水灌溉区水稻田。SP: ¹⁵N的位嗜值。均值混合线:由端元值(SP=-3.90, δ¹⁸O=21.00)、(SP=34.80, δ¹⁸O=43.60)确定; 还原线:斜率为0.35。
Figure4.N₂O production and consumption pathways analyzed by the model of SP-δ¹⁸O of soils of different crop fields irrigated with acid mine drainage and natural water
SG: sugarcane field in acid mine drainage irrigated area; SS: paddy field in acid mine drainage irrigated area; LG: sugarcane field in natural water irrigated area; LS: paddy field in natural water irrigated area. Mixing line is determined by the end-member value (SP=-3.90, δ¹⁸O=21.00), (SP=34.80, δ¹⁸O=43.60). Reduction line is with slope of 0.35. SP: site preference of ¹⁵N.


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图5酸性矿山废水灌区、天然来水区不同作物田土壤硝化/反硝化作用对土壤气体N₂O的贡献比范围
SG:酸性矿山废水灌溉区甘蔗田; SS:酸性矿山废水灌溉区水稻田; LG:天然来水灌溉区甘蔗田; LS:天然来水灌溉区水稻田。Nit:硝化作用; Denit:反硝化作用。
Figure5.Contribution ratio ranges of nitrification/denitrification to N₂O in soils of different crop fields irrigated with acid mine drainage and natural water
SG: sugarcane field in acid mine drainage irrigated area; SS: paddy field in acid mine drainage irrigated area; LG: sugarcane field in natural water irrigated area; LS: paddy field in natural water irrigated area. Nit: nitrification; Denit: denitrification.


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图6酸性矿山废水灌区、天然来水区不同作物田土壤N₂O还原成N₂的比例范围(a)和均值混合线上各点N₂O还原成N₂的比例(b)
SG:酸性矿山废水灌溉区甘蔗田; SS:酸性矿山废水灌溉区水稻田; LG:天然来水灌溉区甘蔗田; LS:天然来水灌溉区水稻田。
Figure6.N₂O-reduction ratio range (a) and N₂O-reduction ratio in the mixing line (b) of soils of different crop fields irrigated with acid mine drainage and natural water
SG: sugarcane field in acid mine drainage irrigated area; SS: paddy field in acid mine drainage irrigated area; LG: sugarcane field in natural water irrigated area; LS: paddy field in natural water irrigated area.


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图7酸性矿山废水灌区、天然来水区不同作物田不同深度土壤气体N₂O同位素特征值δ¹⁵N^bulk与δ¹⁸O线性回归分析
SG:酸性矿山废水灌溉区甘蔗田; SS:酸性矿山废水灌溉区水稻田; LG:天然来水灌溉区甘蔗田; LS:天然来水灌溉区水稻田。
Figure7.Linear regressions for δ¹⁵N^bulk and δ¹⁸O of N₂O in soil air in different depths of different crop fields irrigated with acid mine drainage and natural water
SG: sugarcane field in acid mine drainage irrigated area; SS: paddy field in acid mine drainage irrigated area; LG: sugarcane field in natural water irrigated area; LS: paddy field in natural water irrigated area.


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表1供试土壤含水率、化学性质及其重金属含量
Table1.Moisture contents, chemical characters and contents of heavy metals in the tested soils

处理 Treatment	土壤深度 Soil depth (cm)	含水率 Moisture content (%)	pH	CEC (cmol·kg-1)	全碳 Total carbon (g·kg-1)	全氮 Total nitrogen (g·kg-1)	硝态氮 NO3- (mg·kg-1)	氨态氮 NH4+ (mg·kg-1)	Cu (mg·kg-1)	Zn (mg·kg-1)	Pb (mg·kg-1)	Cd (mg·kg-1)
SG	0~30	17.50±1.93abc	3.92±0.08a	9.69±0.55a	12.94±8.13c	1.41±0.64abcd	47.21±0.75a	2.33±0.22f	332.02±45.86c	297.96±15.61de	271.54±23.65e	0.88±0.06abc
	30~50	17.72±1.59abc	4.29±0.19b	11.32±2.11ab	4.86±0.01ab	0.83±0.03ab	17.39±0.30b	0.85±0.07bc	315.92±68.27c	366.23±73.84ef	241.26±7.74df	1.27±0.04bc
	50~80	14.47±4.56a	4.66±0.07c	14.14±1.21b	4.15±0.52a	0.84±0.15ab	12.40±0.41c	1.36±0.30e	173.62±29.02b	395.89±70.11f	227.05±57.18df	1.70±0.40c
SS	0~30	22.37±4.53bcd	4.28±0.24b	9.52±0.98a	11.53±5.08bc	1.45±0.35bcd	4.28±0.63d	1.31±0.47de	303.83±44.95c	309.90±90.03de	249.49±41.62df	0.57±0.49ab
	30~50	17.15±0.62abc	4.12±0.04ab	9.45±0.73a	5.22±1.16ab	0.79±0.18ab	1.16±0.25e	0.98±0.26cde	396.83±30.34d	304.39±35.54de	238.93±32.88df	1.04±0.04bc
	50~80	15.30±2.68ab	4.26±0.06b	9.74±0.98a	3.81±0.09a	0.70±0.12a	0.85±0.02e	0.90±0.03bcd	317.04±15.97c	275.92±3.97cd	209.55±25.75d	0.94±0.97abc
LG	0~30	21.65±3.05bcd	4.42±0.23bc	18.08±3.17c	8.32±0.72abc	1.03±0.06abc	15.21±0.24f	2.63±0.41f	36.88±3.12a	172.51±30.25ab	68.25±18.13a	0.15±0.01a
	30~50	27.56±0.19d	5.13±0.31d	22.89±0.60d	7.74±0.21abc	1.05±0.10abc	5.84±1.08g	0.57±0.09abc	37.58±3.11a	155.95±22.08ab	47.79±4.72ab	0.14±0.02a
	50~80	26.13±0.77d	5.61±0.08e	23.34±0.09d	7.59±1.15abc	1.31±0.40abcd	3.03±0.26h	0.72±0.15abc	40.67±1.73a	120.32±12.76a	53.80±14.95a	0.10±0.06a
LS	0~30	27.25±5.26d	5.86±0.18e	17.33±1.73c	19.43±4.70d	1.98±0.30d	9.12±1.00i	2.30±0.26f	39.13±3.75a	212.00±14.05bc	136.98±10.72c	—
	30~50	21.87±0.68bcd	6.46±0.01f	18.74±0.36c	10.42±1.37abc	1.63±0.31cd	2.87±0.81h	0.38±0.04a	36.54±1.08a	169.75±6.36ab	138.11±9.74c	—
	50~80	24.14±5.25cd	6.48±0.04f	20.37±2.07cd	9.80±0.69abc	1.39±0.47abcd	4.59±0.28d	0.50±0.07ab	32.65±5.50a	152.00±20.90ab	117.22±26.82bc	—
SG:酸性矿山废水灌溉区甘蔗田; SS:酸性矿山废水灌溉区水稻田; LG:天然来水灌溉区甘蔗田; LS:天然来水灌溉区水稻田。同列不同小写字母表示0.05水平差异显著。SG: sugarcane field in acid mine drainage irrigated area; SS: paddy field in acid mine drainage irrigated area; LG: sugarcane field in natural water irrigated area; LS: paddy field in natural water irrigated area. Data with different lowercase letters in the same column are significantly different at 0.05 level.

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表2土壤反硝化作用贡献比(Denit)、还原比(F_r)及N₂O浓度(c_N2O)与理化性质及重金属浓度的相关性分析
Table2.Correlation coefficients of contribution ratio of denitrification to N₂O (Denit), N₂O-reducation ratio (F_r), N₂O concentration (c_N2O) with heavy metal and physio-chemical properties of soil

	含水率 Moisture content	pH	CEC	全碳 Total carbon	全氮 Total nitrogen	硝态氮 NO3-	Cu	Zn	Pb	Cd	Denit	Fr
Denit	-0.31	-0.60**	-0.41*	-0.10	-0.20	-0.23	0.51**	0.40*	0.43*	0.33	1.00	-0.28
Fr	0.48**	0.31	0.34	0.28	0.34	0.44*	-0.33	-0.65**	-0.49**	-0.67**	-0.28	1.00
cN2O	0.04	-0.14	0.12	-0.21	-0.26	-0.11	0.04	0.04	-0.10	0.14	0.38*	-0.40*
**和*分别表示0.01和0.05水平(双尾)相关性显著。** and * indicate significant correlation at 0.01 and 0.05 levels (2-tailed), respectively.

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